The latter has already been referred to in Chapter II. A further proof of a practical nature was given by Mr. Oliver Bury, the retiring General Manager of the Great Northern Railway in 1912, who then said that after the working arrangement with the Great Central Railway had been entered into, although there had been an increase of 4,000,000 tons of merchandise carried, this additional traffic had actually been worked with a decrease in the goods train mileage of 1,000,000. Apart from all these economies, =the working expenses cannot increase proportionately with the increase of traffic=. Most of the long distance passenger trains now running, except on special occasions or holiday time, could easily hold twice the number of passengers with but little, if any, appreciable increase in the cost of haulage. It must be remembered that a sufficiently powerful locomotive and sufficient coal must be provided for every passenger train, on the assumption that it will be full, whether it leaves with a full complement of passengers or not. Therefore, even though the number of passengers now carried were to be doubled in the case of all Main line trains very little increase in the working expenses would result, certainly not so much as the saving effected by the various economies mentioned. So far as goods traffic is concerned, an increase of 10 per cent. only, as estimated in the tonnage would certainly not cause any great increase in the expenditure. If, on the other hand, the increase of traffic should be very much more than the percentages mentioned (as may very likely be the case), then the revenue derived will be more than sufficient to provide whatever additional working expenses there may be. The expenses of the important items (which constitute probably 50 per cent. of working expenses) of permanent ways, stations, signal boxes, and general establishment charges would not be seriously affected by increase of traffic, only the rolling stock, coal, and part of the staff.